If by "kit" you mean the little prefabs that come flat-packed for you to assemble, you'll find that few people here have a good word to say about them. They are, with few exceptions, undersized, ill-ventilated, and made of very poor quality wood.
Plans vary wildly from very bad to absolutely outstanding.

If you have something specific in mind you can show them to us and we'll evaluate them for you.
Where, in general, are you? Climate matters, especially when it comes to housing.
What level of DIY skills do you have? As a general rule, chicken coops are undemanding, but there are some that are beginner-easy and some that allow a master craftsman to show off.
Here are my Rules of Thumb about chicken coops:
- If it looks like a dollhouse it's only suitable for toy chickens.
- If it's measured in inches instead of feet it's too small.
- If your walk-in closet is larger than the coop-run combo you're thinking of buying think carefully about whether you have an utterly awesome closet or are looking at a seriously undersized chicken coop.
- If it has more nestboxes than the number of chickens it can legitimately hold the designer knew nothing about chickens' actual needs and it probably has other design flaws too.
And some general information:
The Usual Guidelines
For each adult, standard-sized hen you need:
- 4 square feet in the coop (.37 square meters)
- 10 square feet in the run (.93 square meters),
- 1 linear foot of roost (.3 meters),
- 1/4 of a nest box,
- And 1 square foot (.09 square meters) of permanent, 24/7/365 ventilation, preferably located over the birds' heads when they're sitting on the roost.
4 hens
- 16 square feet in the coop. 4'x4' is the only really practical build for this given the common dimensions of lumber.
- 4 feet of roost
- 40 square feet in the run. 4'x10' or 5'x8'. 6'x6' is a bit too small, 6'x8' is more generous and easier to build than 5'x8'.
- 4 square feet of ventilation. A 2'x2' window is theoretically enough, but in practice doesn't create any air FLOW so better to spread the venting around (and even better to exceed the minimums, especially in warm climates).
- 2 nest boxes, to give the hens a choice
6 hens
- 24 square feet in the coop. 4'x6' is the only really practical build for this given the common dimensions of lumber. If you can't walk into it, put the access door in the middle of the long side to make sure you can reach all areas of the coop because a stubborn chicken WILL press itself into/lay an egg in the back corner where you can't reach.
- 6 feet of roost
- 60 square feet in the run. 6'x10' or 8'x8'.
- 6 square feet of ventilation.
- 2 nest boxes, to give the hens a choice